PROJECT SUMMARY/ABSTRACT Thyroid hormone is essential for normal fetal development. Iodine is an essential micronutrient for thyroid hormone production. Maternal hypothyroidism, affecting 2-3% of pregnant women in the U.S., is associated with adverse effects on pregnancy outcomes and offspring neurodevelopment. Iodine deficiency is the leading cause of maternal hypothyroidism worldwide. Although the general population of the U.S. is deemed iodine sufficient, U.S. pregnant women currently have mild iodine deficiency. Exposure to thyroidal disrupting chemicals that interfere with iodine utilization, such as perchlorate and thiocyanate, is of particular concern in vulnerable populations such as pregnant women and their offspring. The proposed studies aim to 1) assess correlations between maternal perchlorate or thiocyanate exposure or iodine status in pregnancy and maternal and newborn thyroid function, 2) conduct a pilot study of associations between maternal exposure to thyroidal disrupting chemicals and iodine status and adverse pregnancy outcomes, and 3) determine associations between maternal thyroid hypofunction and offspring risk of language disorder, a neurodevelopmental disorder with suggested associations with thyroid dysfunction. These findings will have important implications for recommendations for adequate iodine nutrition and for avoidance of exposure to EDC in pregnancy, potentially modifiable risk factors for adverse pregnancy and developmental outcomes. The candidate is an Assistant Professor of Medicine in the section of Endocrinology, Diabetes, and Nutrition at Boston University School of Medicine in Boston, Massachusetts. Her short-term goal is to develop skills in epidemiological studies focusing on reproductive outcomes, environmental epidemiology, and associations between maternal thyroid health and offspring neurodevelopmental outcomes through didactic courses and attendance at national meetings. Her long-term goal is to investigate the effects of maternal EDC exposure in pregnancy on thyroid function and pregnancy and offspring outcomes, using the skills and findings obtained from the proposed studies as the groundwork. The multidisciplinary mentoring team includes experts in thyroidology, iodine nutrition and utilization, reproductive and environmental epidemiology, and pediatric neurodevelopment. Boston University School of Medicine is a recognized leader in groundbreaking medical research. As a part of Boston University, the fourth-largest independent university in the United States, the medical center consortium consists of the Schools of Medicine, Public Health, Dentistry, and the Division of Graduate Medical Sciences along with Boston Medical Center, provides a rich and diverse environment for successful execution of the proposed studies as well as for the candidate's development into an independently funded researcher.